1. Field of the Invention
The present invention relates to a suspendible composition comprising fine particles of a tricyclic compound or its pharmaceutically acceptable salt and a pharmaceutically acceptable surfactant. The suspendible composition according to the present invention is useful as an orally administrable agent or eye drops.
2. Prior Art
Tricyclic compounds as shown by the below-mentioned general formula (I) and pharmaceutically acceptable salts thereof used in this invention have been known to possess excellent pharmacological activities such as immunosuppressive activity and antimicrobial activity, thereby useful for treating and/or preventing rejection against organs or tissue transplantation, graft versus host reaction, various autoimmune diseases and infectious diseases (Japanese Laid-Open Patent Application No. 61(1986)-148181, EP-A-0323042).
Particularly, FR 900506 substance which equals to FK 506 substance, FR 900520 substance, FR 900523 substance and FR 900525 substance are produced by fermenting Genus Streptomyces, in particular, Streptomyces tsukubaensis No. 9993 (FERM BP-927) or Streptomyces hygroscopicus subsp. yakushimaensis No. 7238 (FERM BP-928). Particularly, FK 506 substance represented by the following formula possesses excellent immunosuppressive activity, thus useful for treating and/or preventing rejection against organs transplantation and diseases in the ophthalmology. FK 506 substance: ##STR1## Chemical name: 17-allyl-1,14-dihydroxy-12-[2-(4-hydroxy-3-methoxycyclohexyl)-1-methylviny l]-23,25-dimethoxy13,19,21,27-tetramethyl-11,28-dioxa-4-azatricyclo[22.3.1. 0.sup.4,91 ]octacos-18-ene-2,3,10,16-tetraone.
Injections or capsules for oral use of the tricyclic compound (I) have already been studied. The capsules are generally desirable preparation than the injections from the viewpoint of convenience, but would be difficult to slightly also is not so easy to use for children. Thus, there is a demand for the development of liquid formulations which are excellent in absorption ability when administered orally.
When the tricyclic compound (I) of the present invention is employed in ophthalmology, a concern is caused about the appearance of systemic adverse effect upon its oral administration, intramuscular injection or intravenous injection. Accordingly, eye drops for local administration are preferable in ophthalmology as a formulation capable of reducing the appearance of the adverse effect and attaining the desired object with less administration amount.
The tricyclic compound (I) of the present invention is well-soluble in organic solvents and fats and fatty oils, whereas it is very slightly soluble in water. Therefore, the tricyclic compound (I) is made into oily eye drops or ophthalmic ointments, similar to the general slightly soluble agents, to be used in ophthalmology. However, the oily eye drops or ophthalmic ointments of the compound (I) are disadvantageous in that the tricyclic compound (I) is remarkably poor in penetration into ocular tissues and additionally are accompanied with evanescent paropsia or unadjust pleasantness, thus unpractical.
Consequently, there has arisen a strong demand for the development of eye drops comprising the tricyclic compound (I) and having improvements in penetration into ocular tissues and in the aforesaid drawbacks.